1. Field of the Invention
The present invention relates to the field of manway systems for railroad tank cars and similar containers. Particularly, the invention relates to a manway sealing system with an improved safety collar that facilitates sealing a manway lid against a manway base, thereby reducing the risk of leaks.
2. Description of the Prior Art
Railway tank cars and similar containers for transporting liquids in bulk include manways, or passages through which people or contents may pass into or out of the container. A typical manway includes a flat, disc-shaped lid and a circular base, wherein the lid is pivoted up and away from the base to open the manway and is pivoted down and against the base to close and seal the manway.
The lid is secured to the base via a plurality of eye bolts that are pivotally attached to the base at various points around a perimeter of the base. The lid includes a flat, radially-extending flange corresponding to each bolt, wherein each flange presents an aperture for receiving a bolt. Each aperture includes an outer, narrow aperture neck leading to a broader aperture seat. The bolts are pivoted into the aperture seat through the neck, a washer is placed over the end of the bolt, and a nut is threaded onto the bolt and tightened against the washer to secure the bolt in place.
To prevent inadvertent movement of the bolt out of the aperture seat, a user threads a safety collar onto the bolt so that the safety collar rests below the washer and within the aperture seat. The safety collar is small enough to fit within the aperture seat but is larger in diameter than the aperture neck, thus preventing the bolt from pivoting out of the aperture seat. To open the manway lid, the user loosens the nut until the flange of the lid can be raised above the collar. With the flange above the collar, the bolt can be pivoted out of the aperture and away from the lid.
Unfortunately, the safety collar suffers from various limitations. Because the safety collar is only slightly smaller in diameter than the aperture seat, for example, the flange may snag the collar when the lid is pivoted from the open position to the closed position and rest on the collar instead of the manway base. When this happens, the collar holds the lid slightly above the base and prevents a seal from forming between the lid and the base. Because the lid is held only slightly above the manway base in these situations, it may go unnoticed and left unsealed during transport, thus allowing contents to spill when the container is moved.
Accordingly, there is a need for an improved manway sealing system that ensures a tight seal between the lid and the base.